E-7
PWM (Pulse Width Modulation), which theoretically produces zero quantization noise, a dynamic range that is dependent only on circuit technology, and
feedback all combine to make the MX-D1 a superb high-performance power amp.
In addition, the Yamaha high-performance, high-speed analog and digital LSI chips are designed to optimize the performance of the modulator and
MOSFET drive circuits that form the heart of the MX-D1.
Active power control system
By continuously monitoring the amp's output current and controlling the maximum continuous output power and
instantaneous dynamic power, the MX-D1 always delivers maximum performance with any load impedance between 2 to
8 ohms.
Constant-gain PLL modulator circuit
With a conventional digital power amp, the output is adversely affected by fluctuations in power supply voltage as the
current demands of the amp change. The MX-D1's modulation circuit, consisting of a PLL (Phase Locked Loop) and
modulation circuit, provides a radical solution to this problem.
In response to power supply voltage fluctuations, the constant-gain PLL modulator circuit produces a pulse-width
modulated waveform by modulating the input signal at a suitable rate. In this way, linearity is maintained and the open-
loop gain is fixed, providing stable feedback.
Feedback
Digital output pulses are fed back in a closed-loop feedback circuit, which improves the performance of the modulator
circuit and the linearity of the output stage, providing very low distortion and a wide dynamic range.
In addition, an analog output signal taken from after the LC output filter is fed back to ensure a high damping factor and a
wide frequency response that is unaffected by the load impedance.
Protection system
The protection system, which guarantees safe operation, includes a super-fast current detection circuit that can measure
the current of a single pulse. It also includes safe operating sequential logic, DC detection, and over-current protection.
Switching power supply
Independent, high-efficiency, low noise resonant-type switching power supplies, developed by Yamaha, are used for the
left and right channels.
In addition, the secondary rectifier circuit has a magnetically coupled rectifier, which resolves issues normally associated
with conventional SEPP (single-ended push-pull) digital amps and allows the MX-D1 to always maintain perfect
symmetry between the positive and negative power supply rails regardless of the direction of the output current.
MX-D1_U.fm Page 7 Thursday, June 26, 2003 5:14 PM
